analysis and comparison of regenerative technologies of waste lubricant

Analysis and Comparison of Regenerative Technologies of Waste

Lubricant YU-LUNG HSU 1*

1Department of Resources Engineering National Cheng Kung University

No.1, University Road, Tainan, 701 Taiwan

CHENG-HAW LEE 2 2Department of Resources Engineering

National cheng Kung University No.1, University Road, Tainan, 701

Taiwan VICTOR B. KRENG 3

3Department of Industrial and Information Management National Cheng Kung University

No.1, University Road, Tainan, 701 Taiwan

k r eng@mai l . ncku . edu . tw Abstract: - Lubricant is one of the important resources that cannot be disposed of randomly due to the presence of pollutants. In response to economic efficiency and environmental protection, there is a growing trend of regeneration and reuse of waste lubricant. However, the technologies shall be compared to provide a useful reference for the use of waste lubricant. The major aim of this paper is to analyze and compare the regenerative technologies, thus laying a basis for the governmental bodies in policy-making of lubricant recovery as well as for industrial operators in deciding the recovery methods.

Key-Words: Regenerative Technologies, Waste Lubricant

1 Introduction When additives and foreign substances, such as metal powder, chips and other grease, are mixed into the lubricant, aging, degrading and failure will likely occur, leading to mechanical fault and degraded performance. In such cases, the lubricant is replaced to improve the working efficiency.

The sales volume in the Taiwan lubricant market was registered separately as 400,000 kilolitres and 450,000 kilolitres in 2004, 2005, and the generation rate of vehicle waste lubricant and industrial waste lubricant was 90.6% and 55.6%, respectively. According to the “Planning and Rate Calculation of Waste Lubricant Recovery” formulated by the EPA

WSEAS TRANSACTIONS on ENVIRONMENT and DEVELOPMENT Yu-Lung Hsu, Cheng-Haw Lee, Victor B. Kreng

ISSN: 1790-5079 295 Issue 3, Volume 5, March 2009

mailto:[email protected]

in 1999, vehicle lubricant accounted for about 59.7%, and industrial lubricant for 40.3% of the Taiwan lubricant market. It is thus estimated that the annual yield of vehicle lubricant was about 240,000 kilolitres (45*59.7%*90.6%=24.3), and of industrial lubricant about 100,000 kilolitres (45*40.3%*55.6%=10.0) in 2005.

The efficient recycling of waste lubricant could help reduce both the environmental pollution and gas emission from greenhouses, thus creating a huge efficiency either from environmentally-friendly or economic levels. In addition, the imported lubricant can be cut down since only 1.6 kl of waste oil is required for lubricant extraction. As a two-win measure, waste lubricant recycling and regeneration not only save the cost of lubricant, but also contribute much to environmental protection.

2 Waste lubricant recycling Analysis of pollutant sources of lubricant and disposal. According to the investigation of CSCC, most of the waste lubricants in Taiwan are recycled and reused as secondary oil and fuel (approx. 94%), but the remaining portion leads to environmental pollution (Table 1).

2.1 Potential harmful substances in waste lubricants The lubricant, mainly from oil refining, often generates aggregation, oxidation and acidification due to high-temperature catalysis with metal chips and water during operation. Thus, poly-nuclear aromatics and heavy metals contained in waste lubricant are carcinogenic, inflammable, harmful or corrosive substances (Table 2).

3 Evaluation of the recovery and reuse of waste lubricant in developed countries The waste lubricant must meet environmentally-friendly and application criteria for recovery and reuse. Two key indicators include pollution level and viscosity index in this respect. In Europe, the regenerative oils are classified mainly according to the content of chlorides. Since chlorides are harmful to the human body, and complex finishing processes shall be required during the regeneration process, the chlorine content in reclaimed waste oil shall not exceed 50ppm in EU regulations.

A higher viscosity index of waste lubricant means a higher suitability for regeneration into lubricant. Viscosity is the most important consideration of choosing lubricants. The strength of the lubricant film is approximately proportional to its viscosity, so the higher viscosity indicates the stronger strength of the lubricant film. The viscosity index (VI) refers to the changing degree of viscosity dependent on temperature: the lower V.I means a higher viscosity change in the case of slight temperature change, and vice versa. Thus, in the case of a higher viscosity index, no finishing process shall be additionally required to improve V.I., making it more suitable for recovery and reuse with a relatively smaller operating cost.

4 Comparison of recovery rate between Taiwan and other regions in the world In 2005, there is approx. 340,000 kiloliters of waste lubricant in Taiwan, so the recovery rate is about 4% if the audited statistical recovery yield of 14,000 kiloliters in the same year is divided by 340,000 kiloliters. As compared with European countries, it



is found that Luxembourg had a recovery rate of 39%, and the average recovery rate of Europe was 50% in 2000.

Table 3 lists the predicted recovery rate of some European countries according to their consumption habits and distribution of lubricant. The predicted recovery is obtained by multiplying the consumption with this value. Then, the predicted recovery rate is obtained by dividing the recovery by the predicted recovery.

4.1 Discussion of regenerative technologies The purpose of various regenerative

technologies is to generate reusable lubricant by the following 4 steps.

4.1.1 De-water/de-fuel The main components of light oil contain fuel and naphtha. These foreign substances are mainly leaked from vehicle engines into lubricant, and often disposed of according to their physical characteristics and the properties of the lubricant (boiling point, gravity and solubility).

4.1.2 De-asphalt The solid foreign substances in waste lubricant derive from metal powder and additives during mechanical abrasion, and are often disposed of according to the physical characteristics (solubility and boiling point), or by chemical characteristics (by adding reagent). De-asphalting was previously performed by adding sulfuric acid or solvent, and is now done by means of thin film separation or thermal-finishing.

4.1.3 Fractionation Fractionation separates the substances using the different boiling points and characteristics. The lubricant products are usually a mixture of several organic compounds. So, fractionation is used to select or remove specific substance from the mixture.

4.1.4 Finishing After the aforementioned processes, the finishing process shall be required to remove the remaining foreign substances, such as chlorine, nitrogen, oxygen and sulfur, etc. The finishing process generally comprises clay-finishing or hydro-finishing.

5 Comparison of regenerative technologies The most commonly used regenerative technologies differ a lot from each other with respect to de-asphalting and finishing methods. The previously used technologies include the acid/clay process, the distillation process, and the solvent de-asphalting process, all of which generate acid sludge with secondary pollution. Therefore, reducing secondary pollution is a major consideration of new technologies.

Due to the different finishing methods, there are currently available many new technologies, such as Thin Film Evaporation (TFE), including: TFE + clay finishing, TFE + solvent finishing and TFE + hydro-finishing), Thermal De-Asphalt (TDA), TDA + clay finishing, and TDA + hydro-finishing. In addition, solvent extraction hydro-finishing is developed by means of hydro-finishing after the solvent de-asphalting process. These technologies are described below:



5.1 Acid/clay process First, concentrated sulfuric acid is added into dehydrated waste oil, wherein the foreign substances (e.g. additives and sulfides) will form sludge, enabling 16~48 hour deposition and then separation from the waste oil. The foreign substances, colloid, organic acids and waxy substances are removed by clay (porcelain clay or aluminum silicate) and de-colored. Next, such oil is filtered to yield reusable base oil (Figure 1).

5.2 Distillation process The operating principle of the distillation process is to further purify the waste oil by vacuum distillation prior to the acid/clay process, with its flow process similar to the acid/clay process (Figure 2).

5.3 Solvent de-asphalting process: The propane is used as a solvent to separate insoluble suspended substances such as asphalt, metallic compounds, and resin in the waste oil, with its flow process similar to method 2, other than the solvent extraction and vaporization steps.

In addition to propane, organic solvents, such as propanol and supercritical ethane, can also be used for the solvent de-asphalting process (Figure 3).

5.4 TFE + hydro-finishing This method is used to separate oil and foreign substances via a thin film, and purify it through hydro-finishing to avoid secondary pollution. Firstly, the moisture and light oil contained in the waste oil are removed through hydro-finishing, and then vacuum distillation of free components is required to allow for subsequent separation of a high-

temperature thin film. Finally, the oil is subjected to hydro-finishing to remove chlorine, nitrogen, oxygen, and sulfur compounds (Figure 4).

5.5 TFE + clay finishing This method is used to separate oil and foreign substances via a thin film, and purify it by clay. As compared with TFE + hydro-finishing, the only difference is that the clay is used for absorption in lieu of hydro-finishing (Figure 5).

5.6 TFE + solvent finishing This method is used to separate oil and foreign substances via a thin film, and apply the solvent to finishing, with the flow process similar to TFE + hydro-finishing (Figure 6).

5.7 Solvent extraction hydro-finishing This method combines solvent extraction and hydro-finishing by removing the foreign substances by solvent and then improving oil quality by hydro-finishing. Firstly, the moisture is removed, and the waste oil is separated through propane extraction. Then the mixture of propane and waste oil is subjected to hydro-finishing to remove sulfur, nitrogen and oxygen for purification purposes (Figure 7).

5.8 TDA + clay finishing and TDA + hydro-finishing The dehydrated waste oil is vacuum-heated at 360o. The ash remains at the bottom, and the oil is divided into 3 types: i.e. vacuum gas oil (VGO); base oil (as lubricant); and asphalt residue. Next, the base oil is subjected to hydro-finishing or clay-finishing under



high-pressure (100 bar) for subsequent utilization (Figure 8).

6 Manufacturers for waste lubricant recovery The world-wide leading manufacturers specialized in waste lubricant recovery are listed below:

They are well-proven with long-term development expertise. (1) KTI –focused on TFE + hydro-finishing, with

factories in Greece, Tunisia and the U.S. (2) CEP/MOHAWK.--focused on TFE + hydro-

finishing, with 2 factories in America. (3) SAFETY-KLEEN-focused on TFE + hydro-

finishing, with factories in the U.S. and Canada. (4) Agip Petroli/VISCOLUBE-focused on Thermal

De-Asphalt (TDA) and clay-finishing, with factories in Italy.

(5) IFP--focused on solvent extraction hydro-finishing, with factories in Greece.

(6) SNAM PROGETTI-.focused on solvent extraction hydro-finishing, with factories in Italy.

Well-proven but with little development expertise, are: (1) UOP DCH-laboratory test. (2) New Meinken technology-under development.

7 Comparison and discussion In view of the relative advantages, these regenerative technologies are analyzed comparatively in terms of operational, economic and environmentally-friendly aspects, as listed in Table 4~6. The relational chart of regenerative technologies is depicted in Figure 9, wherein the relationship is explained according to their intersection—based on de-asphalting and finishing technologies. For example, both the distillation and solvent de-asphalting processes

employ clay-finishing, so there is an intersection with the acid/clay process, and so on.

8 Conclusions In a move to achieve environmental protection or sustainable utilization of mineral resources in Taiwan, the recovery rate of waste lubricant should be further improved. In fact, there is much room in this respect according to the economic and technological feasibility aspects. However, the technical feasibility, economic and energy efficiency, as well as possible environmental hazards should be taken into account in any case. Owing to the fact that waste lubricant is possibly disposed at an individual’s own will, or put into the market as new lubricant, it is urgently required to collect the methods and advantages/disadvantages of existing regenerative technologies, establish the recovery and utilization system (for repair depots and factories), formulate the regulatory laws and auditing system as well as the production and consumption system. This would facilitate the planning and management of recovery and sustainable utilization of waste lubricant.

References: [1] Cheng, Y.W., Lin, K.H., Chang, K.H., Huang,

W.R., schedule of “Review of Waste Lubricant Recycling System”, Environmental Protection Agency, Executive Yuan, 2006/1.

[2] Yan, B.W., Chiou, H.H., Lin, J.B., Chang, C.C., Li, J.H., Huang, C.H., “Analysis of Thin Film Evaporation on Lubricant Recycling”, Journal of Petroleum, Vol.37, issue 3, 2001, pp. 65~73.

[3] Bureau of Energy, Ministry of Economic Affairs, Taiwan Energy Resources Statistics Yearbook, 2006.



[4] V. Monier and E. Labouze, Critical review of

existing studies and life cycle analysis on the regeneration and incineration of waste oils. EC-DG Env, Taylor Nelson Sofres and Bio Intelligence Service, 2001.

[5] Willing, A., Lubricants based on renewable resources an environmentally compatible alternative to mineral oil products. Chemosphere, 43, 2001, pp. 89-98.

[6] J. Rincon, P. Canizares, M.T. Garcia, I. Gracia,

Regeneration of used lubricating oil by propane extraction, Ind. Eng. Chem. Res, 42, 2003.

[7] El-Fadel, M., Khoury, R., September, Strategies for vehicle waste-oil management: a case study, Resources, Conservation and Recycling, Vol.33, Issue 2, 2001, pp. 75-91

[8] T. Kalnes, Treatment and recycling of waste

lubricants, A petroleum refinery integration study, paper presented at AICHE Summer National Meeting, San Diego, California: pp. 19-22, 1990.

[9] Ahmad Hamada, Essam Al-Zubaidya, Muhammad E. Fayed, Used lubricating oil recycling using hydrocarbon solvents, Journal of Environmental Managemen, 74, 2005, pp. 153–159.

(Author note: Yu-lung Hsu is incumbent chairman of Taiwan Petroleum Chamber of Commerce, a Ph. D Candidate student of Department of Resource Engineering, National Cheng Kung University)



Table 1�Distribution and hazards of waste lubricant in Taiwan. Distribution Common purpose Percentage Hazards

Recycling dealer Secondary oil and fuel

79.5% Inferior reclaimed oil, leading to mechanical damage

Factories Furnace fuel 14% Inclusive of heavy metal, improper incineration leading to serious pollution

Secondary lubricating in construction

De-molding 2.5% Pollution transfer

Random dumping

4% Serious environmental pollution

Table 2�Potential harmful substances in waste lubricant.

Organic pollutants Possible sources Range polynuclear aromatics Basic oil components (μ g/L) Benzopyrene 360~62,000 Dimethylbenz anthracene 870~30,000

Pyrene 1,670~33,000 Alkyl naphthalene Basic oil components 900,000 Albocarbon Basic oil components 440,000 Chlorine solvent Cleaning agents in

degreasing (mg/kg)

1,1,1- trichloroethane 18~1,800 Trichloroethane 18~2,600 Tetrachlorethylene 3~1,300 Metal elements Barium Additive 60~690 Zinc 630~2,500 Aluminum Engine or metal chips 4~40 Chrome 8~24 Lead Oil 3,700~114,000

Table 3�Recovery rate of lubricant in European regions.

Region Consumption(t) Predicted recoverable rate (%)

Predicted recovery(t)

Actual recovery

Predicted recovery rate (%)

Austria 102,400 44 45,000 33,500 74

Belgium 173,608 44 76,388 60,000 79 Denmark 71,416 65 46,420 35,000 75 Finland 89,194 54 48,165 38,532 80 France 888,771 49 435,498 242,500 56 Germany 1,076,149 50 538,075 460,000 85 Greece 88,000 68 60,000 22,000 37 Ireland 38,900 51 19,839 17,062 86 Italy 681,100 40 272,440 200,395 74 Luxemburg 10,150 50 5,075 2,000 39 Netherlands 154,685 54 83,530 60,000 72 Portugal 113,200 55 62,260 39,620 64 Spain 496,141 55 223,263 105,000 47



Sweden 146,847 54 79,297 63,438 80 Great Britain 803,667 51 409,870 352,500 86 Europe 4,934,228 49 2,405,120 1,731,546 49

Table 4�Comparison of regenerative technologies (operational level).

Process Regenerative technology De-water/de-

fuel De-asphalt Fractionation Finishing Water consumption

Operating temperature

Acid/clay process

Vacuum distillation/centrifugation

Adding sulfuric acid and clay N/A N/A Little Low

Distillation process

Vacuum distillation

Adding clay and a few acids for vacuum distillation

N/A N/A Little High

Solvent de-asphalting process

Vacuum distillation

Adding solvent separation oil and ash

Vacuum heating fractionation

Clay-finishing Little High

TFE + hydro-finishing

Vacuum distillation

Thin film separation (High-temperature/-pressure)


Hydro-finishing Moderate High

TFE + clay finishing

Vacuum distillation

Thin film separation (High-temperature/-pressure)


Clay-finishing Moderate High

TFE + solvent finishing

Vacuum distillation

Thin film separation(High-temperature/-pressure)


Solvent-finishing Moderate High

Solvent extraction hydro-finishing

Vacuum distillation

Adding solvent separation oil and ash


Hydro-finishing Moderate High

TDA Vacuum distillation Thermal finishing Vacuum heating

fractionation

Hydro-or clay-finishing

Much High

Table 5�Comparison of regenerative technologies (economic level). Regenerative technology

Technology maturity

Energy demand

Recovery rate

Quality of reclaimed oil

Equipment demand

Operating cost Scale (kt/y)

Acid/clay process Plant scale Low 63% Poorer* Low Low Small(2~10kt)

Distillation process Plant scale High 50% Poorer* Moderate Low Middle(25kt)

Solvent de-asphalting process

Plant scale High 65-70% API GROUP I High High Middle(25kt)



TFE + hydro-finishing Plant scale High 72% API GROUP II High

High Big(50~80kt)

TFE + clay finishing Plant scale High 72%

API GROUP II High

High Big(100kt)

TFE + solvent finishing Plant scale High 72%

API GROUP II High

High Big(100kt)

Solvent extraction hydro-finishing

Plant scale High 74% API GROUP II

High High Middle(60kt)

TDA Plant scale High 74-77% API GROUP II High

High

Big(100~180kt)

*Acid/clay and distillation processes were developed previously. The regenerated substances couldn’t meet the present criterion of base oil.

Table 6�Comparison of regenerative technologies (environmental-friendly level). Regenerative technology Acid sludge Residual oil

sludge Harmful chemicals Secondary pollution

Acid/clay process Much Much Sulfuric acid Yes Distillation process Little Many Sulfuric acid Yes Solvent de-asphalting process Little Much Sulfuric acid and volatile

organic solvent Yes

TFE + hydro-finishing N/A Little N/A Few

TFE + clay finishing N/A Little N/A Few

TFE + solvent finishing N/A Little Volatile organic solvent Few

Solvent extraction hydro-finishing N/A Little Volatile organic solvent Few

TDA N/A Little N/A Few



Waste oil

Acid-finishing

Dehydration

Deposition

Clay finishing

Filtering

Base oil

΅ BWater light oil

Sulfuric

΅ B ΅ B Acid gas, sludge

waste solution

Clay

Waste clay

Waste oil or light oil is separated by means of gravity or heating

Improve the color of ΅ B reclaimed oil by

aggregation and neutralization

Acid sludge is separated

by deposition

Remove foreign substances in waste oil

Separate reclaimed base oil and waste clay

Fig.1�Schematic diagram of the acid/clay process.

Fig.2�Schematic diagram of the distillation process.

Dehydrationand removal of

light oil

Vacuumdistillation

Clay finishing

Base oil

Residue and major pollutants

Waste clay and acid

Waste oil

Purify the waste oiland remove foreign

substances

Remove organic acid and de-color

Remove the moisture and light-boiling substances

in waste oil Water, light oil



Waste oil

Vacuum dist illation

Dehydration removal of light oil

Solvent extraction

Centrifugation

Stripping

Vacuum dist illation

΅ B Water light oil

Fuel

Supplementary

Sludge

Bottom oil

Remove residual water and light-boiling substances

The propane is used asseparate suspended

in the oil

Centrifugal machine is used to separate upper extract and

lower insoluble residue

The propane solvent is recycled by

stripping and heating

Clay finishing

Base oil

΅ BWaste acid waste clay Remove organic acid in

Oil and decolor

Fig.3�Schematic diagram of the solvent de-asphalting process.



Dehydration removal of light

Vacuum

¥ Υ¤ g³ B² z

Base oil

Residue a nd major

pollutants

΅ B Ό o¥ Υ¤ gΌ o» Δ

Thin film vaporizer is used to remove foreign substances

Remove organic acid in waste

and decolor

Waste oil

΅ BWater light oil Remove moisture and

light-boiling substances in waste oil

Filtering

Filter completely to separate ΅ A reclaimed oil and

oil sludge

Hydro-finisNitrogen, oxygen and

sulphur compounds

Fig.4�Schematic diagram of TFE + hydro-finishing.

D ehy dration removal of light oi l

Th in fi lm

Clay-finish ing

Base oil

Res idue and major

p ollutants

΅ BWaste clay waste acid

Thin film vaporizer is used to remov e fo reign substances

Remove organic acid in waste oil and decolor

Waste o il

΅ B Water l ight oi l ¥ Ψ� Ί¦ b© σ¥ h° £

Ό o� o¤ ¤� Ί¤ τ¥ χ¤ Ξ » �́ m� «

Filtering

Fil ter completely to separate ΅ Areclaimed oil and

an d oil s ludg e

Fig.5�Schematic diagram of TFE + clay finishing.



Dehydration removal of light oil

Thin film

¥ Υ¤ g³ B² z

Base oil

Residue and major

pollutants

΅ BΌ o¥ Υ¤ gΌ o» Δ

Thin film vaporizer is used to remove foreign

Remove organic acid in waste oil and decolor

Waste

΅ BWater light oil

Remove

Moisture in waste oil and decolor

Filtering

Filter completely to separate ΅ Areclaimed oil and

oil sludge

Solvent-finishin

Fig.6�Schematic diagram of TFE + solvent finishing.



Fig.7�Schematic diagram of solvent extraction by hydro-finishing.

Waste oil

dehydration and removal of light oil

Vacuum distillation

solvent extraction

centrifugation

stripping

vacuum distillation

hydro-finishing

base oil.

water, light oil

Fuel

supplementary solvent

sludge

bottom oil

Remove residual moisture and light-boiling

substances

The propane is used as a solvent to separate

suspended substance in oil

The centrifugal machine is used to separate

the upper extract and lower insoluble

residues

Propane solvent is recycled through

stripping and heating



Was te o il

Dehyd ration an d rem oval of light oil Water and light oil

Heating

Lig ht d iesel oil Lubricant Heavy asp halt oil

Hyd ro -finis hin g de-as ph alt in g

Base oi l

Remo ve foreign sub stances s uch as

metal

Disti ll into three

parts

Fig.8�Schematic diagram of TDA finishing process.

Fig.9�Relational chart of regenerative technologies.



analysis and comparison of regenerative technologies of waste lubricant

Documents

industrial lubricant

industrial waste lubricant

reuse of waste lubricant

lubricant extraction

imported lubricant

cost of lubricant

taiwan lubricant market

waste oil